Method of making fluted drill and the like



April 7, 1970 MASAO MAKINO ET AL 5 9 METHOD OF MAKING FLUTED DRILL ANDTHE LIKE Filed Aug. 21, 1967 2 Sheets-Sheet 1 flmawo mm 1 mumznk/ 775590 I n venlorg By Attarneyg April 7, 1970 MASAO MAKINO ET AL METHOD OFMAKING FLUTED DRILL AND THE LIKE 2 Sheets-Sheet 2 Filed Aug. 21, 1967FIGZ In venlor;

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United States Patent 3,504,575 METHOD OF MAKING FLUTED DRILL AND THELIKE Masao Makino and Muneaki Tesaki, Akashi, Japan, assignors to KobeSteel Ltd., Fukiai-ku, Kobe, Japan Filed Aug. 21, 1967, Ser. No. 661,976

Claims priority, application Japan, Oct. 3, 1966,

41/ 65,260 Int. Cl. B21k 5/02 US. Cl. 76108 3 Claims ABSTRACT OF THEDISCLOSURE A method of making drills and the like having oil passagestherein comprising boring holes, which are several times as large indiameter in cross-section as the oil passages in the intended drill orthe like, in a thick stock material which is several times as large incrosssection as the intended drill or the like at required places,heating the stock material, forging or rolling the same by any methodfor forming them into an elongated intermediate stock materialcorresponding in diameter to the intended drill or the like, andfinishing it by any method to provide a drill or the like having oilpassages therein.

This invention relates to a novel method of making drills having in theinterior thereof narrow oil passages extending in the direction of theedges. The invention is not limited to drills but also applicable to themanufacture of reamers and taps, these being herein generically referredto as drills and the like.

Such a drill has generally two very narrow oil passages leading from thefront end to the shank, and these oil passages pass through the interiorof the drill helically along the helical edges (refer, for example, toUS. Patent No. 3,073,189). It is, therefore, generally impossible tobore oil passages after manufacture of the drills, it being usual tobore them linearly in the drill stock material prior to the twistingstep. In general, such drills with oil passages are produced in such aWay that two narrow holes (usually 1.53.0 mm. in diameter) of the samediameter as that of the oil passages in the final product are linearlybored in a cylindrical steel stock material of substantially the samesize as the intended drill diameter and the stock is then subjected tofiuting operation and finally twisted. However, boring a very narrowhole such as oil passage in a steel stock of considerable length(usually 250-400 mm.) is no easy task and the efiiciency of manufactureis very low. Of course, narrow holes themselves do not require any highaccuracy in dimensions, since they have only to allow oil to passtherethrough. However, offset boring conditions such as, for example,two narrow holes being contacted with each other or deviated toward theouter peripheral surface or flutes of the drill are undersirable.Therefore, this boring operation on steel stocks requires relativelyhigh skill and carefulness. In fact, the conventional methods have.involved a considerable amount of waste articles.

The invention aims to rationalize the manufacture of drills and the likehaving narrow elongated oil passages difficult to bore by the usualmethods, by providing a method entirely different from the conventionaltechniques, and it is characterized by using as a stock a steel materialsuch as a round bar billet or ingot thicker than the intend finalproduct, boring large holes in said thick stock, heating and subjectingit to extrusion, forging or rolling by any suitable machines includingpresses, hammers, swagers and rolls for stretching it to a desireddiameter, followed by the conventional processes for finishing it into adrill or the like.

Further, according to the invention, the large holes "ice bored in thethick stock material may be filled with a heat-resistant powder orgranular medium or low melting point material and then sealed so thatthe holes can be advantageously prevented from being excessivelydistorted in the subsequent stretching operation.

Further, according to the invention two or more thick stocks havinglarge holes bored therein may be welded in series to provide anintermediate stock, thus making it possible to make a number of drillsand the like by stretching said intermediate stock.

These and other objects and features of the invention will appear fromthe following description with reference to the accompanying drawings,in which:

FIGS. 13 are flow sheets showing the sequence of steps for embodying thepresent method.

Referring to the drawings, a square or round billet 1 which is severaltimes as long as the intended drill is prepared (FIG. 1, I). Holes 2Which are several times as large in diameter as the oil passages in theintended drill are bored in this billet axially thereof at suitable.places (FIG. 1, II). The boring may be very easily effected with theordinary degree of technique by using a usual boring or drilling machinewithout requiring any special technique and carefulness. If necessary, aheat-resistant powder or granular medium 3 such as hard carbon andalumina is stuffed in said large holes 2 with a suitable degree ofstufling hardness (FIG. 1, II) and the opposed ends of the holes arethen suitably sealed. The billet is then heated to a working temperatureand either forged by a press, hammer o-r swager or rolled, therebydecreasing the diameter and increasing the length to provide anelongated intermediate stock material 4 corresponding in diameter to theintended drill (FIG. 1, III). In this forging or rolling operation, thelarge holes 2 in said thick stock material 1 are squeezed whileretaining the medium 3 stuffed therein, so that they are transformedinto narrow holes 5 (FIG. 1, III). These holes have the same narrownessor diameter as the oil passages in the intended drill. In this case, ifthe stuffing medium 3 is employed, the support action thereof willprevent the large holes 2 from being excessively distorted when they aretransformed into narrow holes 5. Then, the seals are removed (or thestock material is slightly out or turned at the opposed ends thereof) totake out the medium 3. Thereafter, required flutes 6 are formed in theintermediate stock material 4 on the opposed sides (FIG. 1, IV) and thematerial is finished as by twisting by the known method to provide thefinal product (FIG. 1, V).

FIG. 2 shows another mode of embodying the invention, where a shortbillet 11 which is several times as thick as the intended drill isprepared and holes 12 which are several times as large in diameter asthe intended oil passages are bored therein at suitable places, therebyproviding a stock material (FIG. 2, I). Then, a number of such stockmaterials are fused at 13 in series as by electric resistance welding toprovide an intermediate stock material (FIG. 2, II) which is long enoughto produce a number of final drills therefrom, the welds 13 beingsubjected to boring so that the holes 12 may penetrate throughout thelength. Thereafter, the intermediate stock material is subjected tostretching or drawing several times at ordinary temperature fordecreasing the diameter and increasing the length, thereby providing anelongated secondary intermediate stock material (FIG. 2, III).Thereafter, twisting operation may be applied thereto to form it into adesired drill (FIG. 2, III-V).

As fully described above, according to the method of the invention largeholes previously bored in a stock material having a diameter severaltimes as large as that of a final drill or similar product are finallytransformed into narrow holes, so that there is no need of boring narrowholes of the same diameter as the oil passages as in the conventionalmethods. Moreover, boring such large holes in short stock materials isvery easy in view of machining technique involved. Further, as there isno danger of causing offset as in boring of narrow holes, two oilpassages in a final drill or similar product have maintained thedistance therebetween, without deviation toward the outer periphery,thus effectively contributing to the passage of oil.

EXAMPLE 1 A round steel bar 21 which is 21 mm. in diameter and 232 mm.in length is prepared and two round holes 22 with a diameter of mm. arebored therein with a drill from one end for a length of 140 mm., theterminal ends of the holes being communicatively interconnected by atransverse hole 23 (-FIG. 3, I). Then copper wires 24 and 25 areinserted in the round holes 22 and transverse hole 23 and the ends ofthese holes are sealed by plugs 26 and 27 (FIG. 3, II). The portion ofthe round steel bar in which the holes exist is dipped in a salt bathand heated to about 1,000" C., whereupon said portion is passed in atwist die for extrusion, thereby providing an intermediate producthaving a diameter of 16 mm., about 220 mm. long edge portion 28 andabout 130 mm. long shank portion 29 (FIG. 3, III). Subsequently, it ishardened at about 1220 C., whereupon the copper wires are melted to flowout. Finally, it undergoes the usual turning and grinding operationswhereby it is finished into a drill (FIG. 3, IV).

EXAMPLE 2 A round steel bar 11 which is 18 mm. in diameter and 230 mm.in length is prepared and two round holes 12 with a diameter of 5.5 mm.are bored therein with a drill throughout the length thereof with aspacing of 8 mm. between the holes (FIG. 2, I). Then, a suitable numberof such bored round steel bars 11 are joined in series by welding 13 andthe joined portions being bored to break through the round holes 12(FIG. 2, II). It is then annealed and drawn. The drawing operation iseffected at a temperature of ZOO-300 C., using a lubricant oil, inseveral steps, followed by an intermediate annealing and it is finallyworked into a long-sized round steel bar 14 having a diameter of 10.5mm. (FIG. 2, III). Then, this long-sized round bar is cut ito lengths of300 mm., each being subjected to drawing operation to provide along-sized round steel bar haw'ng a diameter of 8.0 mm Then, thislong-sized round steel bar is cut into lengths of 500 mm. to provide thefinal stock materials 15 (FIG. 2, IV), whereupon they undergo the usualoperations including inverse lead cutting, twisting, fiuting, hardening,tempering and heading, whereby they are finished into tapered drills 16having oil passages 17 (FIG. 2, V).

While particular embodiments have been shown and described herein, it isto be understood that the invention is not limited thereto but shallcover and include any and all modifications which fall within the scopeof the invention as hereinafter claimed.

What is claimed is:

1. A method of making drills and the like having oii passages thereincomprising boring holes, which are several times as large in diameter incross-section as the oil passages in the intended drill or the like, ina thick stock material which is several times as large in crosssectionas the intended drill or the like at required places, heating the stockmaterial, forging or rolling the same by any method for forming theminto an elongated intermediate stock material corresponding in diameterto the intended drill or the like, and finishing it by any method toprovide a drill or the like having oil passages therein.

2, A method as claimed in claim 1 wherein a heatresistant powder orgranular medium or low melting point metal is stufied in the large holesin the thick stock material and the holes are then sealed, said mediumor metal being removed later.

3. A method as claimed in claim 1 wherein a number of thick stockmaterials having large holes bored therein are lengthwise joined bywelding.

References Cited UNITED STATES PATENTS 2,541,849 2/1951 VilleneuveBERNARD STICKNEY, Primary Examiner US. Cl. X.R. 72-464

